Production of ammonium thiocyanate



Patented June 16, 1942 PRODUCTION F AMMONIUM THIOCYANA'EE William H. Hill, Stamford, Conn., assignor to American CyanamidCompany, New York, N. Y., a` corporation of Maine Application August 25, 1939, Serial No. 291,815

Claims. (C

The present invention relates to the production of ammonium thiocyanate by reaction between liquid carbon bisulide and liquid ammonia. It has been determined that lthe lreaction between thesetwo substances gives rise toa yellow product containing S and N in the proportions of 2:3 and identified only as having most likely an empirical formula. corresponding to HsCzNaSz, and also to ammonium dithiocarbamate and ammonium thiocyanate. The production of the yellow compound and ammonium dithiocarbamate occurs only at temperatures below 40 C. Above that temperature, the end product is ammonium thiocyanate although the iirst two compounds mentioned may be formed at an intermediate stage. l

In other words, even though the reaction takes place, for instance, at 33 C., which favors the production of the yellow compound, yet raising the temperature of the reaction magma in ammonia or in ammonia containing ammonium thiocyanate, causes conversion to ammonium thiocyanate.

These higher temperatures for the conversion to the thiocyanate may be applied under pressure as indicated in Fig. 1 in the iiow sheet, where the initial medium is substantially only excess ammonia and such quantities of ammonium thiocyanate as are gradually produced. On the other hand, by introducing sufl'lcient quantities of ammonium thiocyanate into the liquid ammonia, the vapor pressure of the liquid ammonia may be depressed to such an extent that tem'- peratures as high as 80 C. may be obtained at atmospheric pressure. Thus any desired temperature between the boiling point of NH3 and 80 C. may be obtained by varying the content of thiocyanate.

The preferred method, therefore, of reacting carbon bisulde in excess liquid ammonia to produce optimum yields of thiocyanate with minimum diiculties is as shown in Fig. .2' of the iiow sheet, to begin with an initial solution of liquid ammonia containing appreciable quantities of ammonium thiocyanate at the boiling point thereof. To this solution is added a deficiency of carbon bisulflde and the whole gradually heated. Temperatures up to the critical temperature of liquid ammonia are usable, although those not over 80 C. are preferred. Under these circumstances, the initial yellow slurry obtained as a result of the reaction gradually changes. color and nnally is converted to a clear thick syrupy liquid. Evaporation'ot this liquid expels not only ammonia but some hydrogen sulde with the production of lclear monoclinic crystals of ammonium thiocyanate in substantially quantitative yields.

By returning some of the recovered vthiocyanate to the reaction vessel with fresh ammonia, a cyclic method results.

While the invention has been shown and described with particular reference to specific embodiments, it is to be understood that it is not to be restricted thereto but is to be construed broadly and limited solely by the scope of the .appended claims.

I claim:

1. A method of producing. ammonium thiocyanate from liquid carbon bisulde and liquid ammonia which comprises reacting the materials at temperatures above 35 C., evaporatingthe liquidproduct and recovering the solid ammonium thiocyanate.

2. A method of producing ammonium thiocyanate from liquid carbon bisulde and liquid ammonia which comprises reacting the same to form a voluminous yellow precipitate and heating the reaction magma under pressure to convert the yellow lproduct to ammonium thiocyanate. f

3. A method of producing ammonium thiocyanate which comprises reacting carbon bisulfide and ammonia in the initial presence of sufcient quantities oi ammonium thiocyanate so that a. temperaturel between the boiling point of ammonia and C. may be obtained in the reacting magma at atmospheric pressure, and carrying out the reaction at that temperature' and that pressure until substantially quantita'- tive conversion to ammonium thiocyanate has taken place.

4. A method of producing ammonium thiocyanate which comprises reacting carbon bisulf .fide and ammonia in the initial presence of ammonium thiocyanate, heating to eiect a conversion of the reaction products to ammonium thiocyanate and recovering the latter.

5. A method ofproducing ammonium thiocyanate which comprises reacting carbon bisulflde and ammonia in the initial presence of ammonium thiocyanate'heating to e'ect a conversion of the reaction products to ammonium thiocyanate and recovering the latter and returning some of the thiocyanate to the start ofthe cycle.

' WILLIAM H. HILL.' 

